In healthy individuals, the creation of a wound induces an initial vigorous angiogenic response, ultimately creating a vascular density that far exceeds that of normal uninjured tissue. During the resolution phase of healing, the majority of these new vessels disappear, and the vessel bed is pruned back to normal density. The healing wound therefore provides an excellent model for the study of the regulation of angiogenesis. Recent studies by both us and others rather unexpectedly suggest that a partial inhibition of the exuberant wound angiogenic response can improve healing outcomes in normal skin wounds. In concert with this, our studies also show that wounds that heal quite perfectly, such as those produced in oral mucosa and in early gestation, exhibit a reduced angiogenic response when compared to adult skin wounds. The concept that most skin wounds display an unnecessary over-amplification of capillary growth represents a paradigm shift, as substantial capillary growth has always been thought to be essential for optimal repair. However, many of the vessels that are produced in the forceful proangiogenic phase of healing are immature, and incomplete anastamoses seem common. A reduced response might create a refined yet highly functional vascular bed that fully supports repair processes. These findings suggest that a complete understanding the regulation of wound angiogenesis has important implications. The long-term goal of this research is to understand the regulation of wound angiogenesis, and to decipher the impact of this process on wound healing outcomes. While the proangiogenic factors in wounds are well-described, less is known about the anti-angiogenic factors that regulate vascular regression. Recently we identified pigment epithelium-derived factor (PEDF) and vasostatin-1 (a fragment of chromogranin A) as anti-angiogenic factors that are produced in wounds and likely to play a role in the regulation of wound angiogenesis. Aim 1 will characterize the expression patterns of these candidates in healing murine wounds. To assess clinical relevance, the production of PEDF and vasostatin-1 will be examined in parallel experimental wounds in mice and humans. Aim 2 will use nanotechnology-siRNA and Ab neutralization approaches to establish a functional role for each factor in directing capillary regression in the resolving woun. Aim 3 will examine how overly robust angiogenesis negatively affects healing outcomes. The experiments will study several characteristics of rapidly developing capillary beds (edema and poor perfusion), and of regressing vasculature (apoptotic load) that might influence healing responses. The proposed studies will advance our knowledge of the angiogenic control mechanisms that are in place in normally healing wounds, and will address novel hypotheses about how the tremendous capillary growth that occurs in skin wounds shapes the healing process. The impact of these studies lies in their application to situations of disregulated angiogenesis (both too much and not enough), including non-healing wounds, malignancies, inflammatory diseases, scar formation, and tissue fibrosis. PUBLIC HEALTH RELEVANCE: A remarkable facet of wound healing is the growth of new blood vessels. As tissue heals, new blood vessels fill the wound space, ultimately reaching a density far greater than normal uninjured tissue. With time, though, most of these new blood vessels disappear, and eventually the vessel density returns to normal levels. The goal of this project is to understand what factors regulate the growth and disappearance of blood vessels in wounds. The findings will help us devise new therapies to correctly modulate this process and improve healing capacity.